Spark generation



Sepf 3, 1957 E. G. LINDEN 2,805,366

SPARK GENERATION Filed Oct. 4, 1954 FIG.2

INVENTOR.

ERIK G. LINDEN /4/7 0/we y United States Patent SPARK GENERATION Erik G. Linden, Red Bank, N. J., assignor to the United States of America as represented by the Secretary of the Army Application October 4, 1954, Serial No. 460,282

3 Claims. (Cl. 315-240) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to spark generators and more particularly to a spark generator wherein the time of sparking may be predetermined and delayed.

. It is a primary object of the present invention to provide a spark generator wherein the desired spark may be produced at a predetermined time or delayed.

It is a further object to provide a spark generator comprising an electret powered sparking device and a trigger mechanism therefor.

In accordance with the present invention, there is provided a spark generator comprising a body of dielectric material having relatively permanently positively and negatively charged opposite faces, and induction member in substantially abutting arrangement with each of said faces, an electrical conductor which is readily broken for connecting said induction members, means for breaking said conductor, and spark gap means associated with said induction members whereby the breaking of said conductor results in a movement of said members away from said body and a spark across said gap. I

Also in accordance with the presentinvention, there is provided a disc of electret material, an induction plate on each face of the disc, a loop of readily breakable electrically conducting wire for connecting the plates and maintaining them on the disc, means for breaking the wire and spark gap means associated with the plates whereby the breaking of the wire results in a movement of the plates away from the disc and a spark across the gap.

For a better understanding of the present invention together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawing,

Fig. 1 is a view, partly in section, of a preferred embodiment of the device prior to sparking; and

Fig. 2 is a view of the device of Fig. l, partly in section, at the instant of sparking.

Referring now more particularly to Fig. l, a disc 4 of electret material has on or close to each face thereof, induction plates 6. The electret material may be any such material well known in the art, examples of which are a composition comprising 50% carnauba wax and 50% resin, a polymethyl methacrylate resin, such as the commercial product, Plexiglas, or a polyvinyl acetate resin such as the commercial product, Gelva 7, manufactured by Shawinigan Chemicals, Limited. The area and thickness of disc 4 are not critical. Preferably, disc 4 may be of substantially circular outline with a diameter of about 3 inches or may be of polygonal configuration. Its thickness may be of any suitable amount, being preferable. Plates 6 preferably consist of an electrically conductive metal such as copper, brass, tin, zinc and the like and may be of any thinckness such as that ranging ICC from thin foil to a thickness of about Vs". The area of plates 6 need not be co-extensive in area with that of disc 4. It is preferable, at least, for one of plates 6 to be of lesser area from that of disc 4. Connecting plates 6 is a loop of readily corrodible or breakable wire 8 which may consist of a materialreadily corroded by acid such as copper, zinc or brass. Wire 8 may also consist of a material having a low melting point such as a low melting alloy, as for example, bismuth alloys and the like, a carbon loaded electrically conductive wax or such as Johnson Wax No. 50 Black made by S. C. Johnson & Son, Incorporated, a thermoplastic resin having good electrical conductivity, such as set forth in Shawinigan Chemicals, Limited Catalog entitled Shawinigan Acetylene Black, copyright 1946. Wire 8 in addition to serving as an electrical conductor between plates 6 may also serve as a mechanical support to maintain plates upon disc 4 prior to sparking. Wire 8 may be attached to a plate 6 by solder or one end may be soldered to one plate and a second end may be held in contact with the other plate by such means as a clip spring (not shown) and the like. In addition to the mechanical support provided by wire 8 in maintaining plates 6 on disc 4, the plates may be maintained in position by other well known means (not shown) such as by springs having one end aflixed to a non-conductive member in the chassis wherein the device is contained and the other end bearing against a plate 6. In contact with each plate6 respectively are ends of wires 10, wires 10 consisting of an electrically conductive material. The other ends of wires 10 terminate in opposed relationship with a small spark gap 12 therebetween. Where the device is to be used in one-shot operation, wires 10 may consist of a metal such as copper, tin, brass, etc. However, where repeated operation of the device may be desired, it is preferable for wires to consist of a material that is more heat and corrosion resistant such as tungsten and the like.

Considering now the operation of the device, it is known that electrets consist of a dielectric material which possesses the property of substantially permanently retaining an electric charge impressed thereon, and that when such a charge is applied thereto, the electret undergoes a volume polarization. If one side of disc 4 is positive and the other negative, upon placing induction plates 6 thereon as hereinabove described, and connecting them With wire 8, a charge is provided on plates 6 which is opposite to the charge of the respective faces of disc 4 upon which the plate rests. This may be explained as follows. Upon placing a plate 6 on the positive face of dies 4 the negative ions are attracted and the positive ions are repelled to the distal surface of the plate. The same phenomenon occurs with the plate placed upon the negative face of disc 4 with the difference, of course, being that the positive ions are attracted to disc 4 and the negative ions are repelled therefrom. Upon connecting plates 6 with wire 8, a momentary flow of electrons takes place between the plates to neutralize the charges on the distal surfaces due to repelled ions. Thus, there remains the negative charge on the plate next to the positive side of disc 4 and a positive charge on the plate next to the negative side of disc 4. Upon breaking wire 8 and moving one or both plates away from disc 4, the plate or plates 6 are freed from the electric attraction of disc 4 and the charges thereon are neutralized by a spark across gap 12.

To permit a better understanding of the invention, the

following examples of the embodiments of the invention are presented by way of illustration.

Example I Wire 8 is made of a readily corrodible metal such as copper or zinc which by its mechanical action supports 1,3 d q ps Pla :6 apla e 29. t s f..,d, s,.4.- v .A drop of sulfuric acid or aqua regia is placed upon wire 8. Under the action of the acid, wire 8 is destroyed by corp q breaking t s a i st Qa. FiWQ Jl pl t s 6 endure; fi f e-ii a asuvaq fo p at s 6 w e up n i s l'h h o th P a s m ve, aw -from d s a d1 sparlgjis generated; The movernent of induction plates 6 after destruction of wire 3 may be produced by the action i F Y a ra nt n qtqth me i a c ion: The time at which the sparking takesplaeecanbe regulated quite accurately by varying thethiekness of Wire 8 or by varying the strength and amount of acid used.

7 Example '11 In this example, wires consis t s of a low melting alloy suh asi1ea eue wire, a bismuth alloy, anelect ally coiidiicting (wX,,.1oaded with. conductiye carbon black) or ajthermoplastic electrically conductive resip, W 18. f sibf h By I at H a hier su lhe jt a Being-produced, forexample, by an exothermic ehemical reactipn heatin g system such as a system composed of iron, ammonium chloride,. cupric oxide and water as disclosed. in U. S. Patent 1,502,744 to rename issued on July 9 ..19.. 4-: .I. 'u a, ys i e l i v ly ig hieatover short iodis desired, a comparatively small amount of water is added wh reashadqtti of larger amounts of water produces a lower heat over a longer period Another sample .a unit set forth in Chemical and En gineeririg Newsjf vol. 30, May 12, 19 2, page 1992. p The action of the device after destruetion ot wire 8 is the same as ofitlinfid in Example I. By controlling the exoheating system, the time of sparking may be predetermined. V

v Exa m ple lll In this example, the materials and action are substantially the same 'as that set forth in Example II except that the heat is supplied by a system consisting of a solution of salts in their water of crystallization. Su'c'ha system is disclosed 'in U. S. Patent 1,385,074 to Ferguson and may consist of a water of crystallization solution "of sodi um acetate and sodium thiosulfate. In such a system, under the impulse of mechanical vibration, for jarring, the salts crystallize out of solution giving ofi heat in the process. 7 a I 1 V a i In Fig. "2, there is shown the position of the various 4 e emen o t e, evice ,attb momen t a Wire .8 is.v destroyed, with the lower induction plate 6 moved away from disc 4 and a spark across gap 12.

The present invention is an inexpensive time delay device which finds useful application in triggering events such as explosions, data; recording apparatus, etc. In those situations, where the device oanbe recovered, it merely requires replacement of wire 8 to permit reuse h r f. H v ,7 J 1.

While there have been described what are,"a-t present, considered to be the preferred embodiments of this invention, it will be obvious. to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and, it is, therefore, aimed in the, appended claims to cover all such changes and modifications as fall within the truespirit and scope of the invention.

What is claimed;

. 1.. A, spar fi d v fioi'ltiine delayed of events by a spark cijmpris'ing, anjelectret kept shortcircuite'd by induction plates on oppo'si'tefa'ce s of said electret, 'saidpla'ties' being mechanically held in place an electrically co iductiri 11'6 of a carbon loaded thermoplasticresin that shor cuitssaid plates, an efro'tlieirnic chemical he ing sys: a means forb reakin g said Wire withinapredetermiiied p erio dbf time, and spark gap means assoi'afted with said induction plates whereby thebi eakirig'of said wire results in' a movement of one of said plates away from one face of said electret said movement energizing the spark that is to trigger the event. 7 2. A sparkgeaeram as fdefinedin' claim 1 whereinsaid chemical heating system comprises a composition consis'ting orfs'odin acetate'and sodium thiosulfate dissolved in their waferof crystallization, said heating composition emitting heat uponmec'hanic'al vibration. 3. A spark gen rate: 'as defined in 1, said chemical heating system comprises iron, ammonium chlr'ide, ClibficfiXid add water. l

'lhe Eleetretj Gutman. Reviews of Modern Physics, vol. 20, No. 3, July 1948, pages 457-71. 

